Rahman syndrome is a rare autosomal-dominant intellectual disability syndrome caused by monoallelic pathogenic frameshift variants affecting the C-terminal domain (CTD) of the HIST1H1E gene. HIST1H1E is a single-exon, intronless gene located on chromosome 6p22.2. It encodes the linker histone H1.4, a member of the H1 histone family, and functions as a structural component of chromatin to control DNA compaction, gene expression regulation, DNA replication, recombination, and repair. The HIST1H1E protein contains an N-terminus region enriched in basic amino acids, a central conserved globular H15 domain involved in DNA binding, and a long Cterminal tail enriched in lysine, serine, and proline. 1 This condition, also known as HIST1H1E syndrome, was first described in 2014 and is characterized by overgrowth, distinctive facial features (full cheeks, high frontal hairline, hypertelorism, telecanthus, deep-set eyes, downslanting palpebral fissures, micrognathia, etc.), intellectual disability (mostly moderate severity), and behavioral problems. Other symptoms include strabismus, hypothyroidism, cryptorchidism, skeletal and cardiac anomalies, abnormal dentition, hypotonia, and abnormal brain MRI with corpus callosum abnormalities being the most frequent finding. 2,3 Additionally, autism spectrum